Novel plant-based yoghourt and preparation method thereof

Abstract

The invention discloses novel plant-based yoghurt and a preparation method thereof, and belongs to the technical field of yoghurt preparation. The preparation method comprises the following specific steps: (1) rehydrating and swelling dry corn kernels, and performing wet grinding to obtain corn steep liquor; (2) adding flavourzyme, glutamine transaminase and alpha-amylase, and carrying out enzymolysis; (3) adding glucose, white sugar, vegetable oil, gel protein, an emulsifier and a stabilizer to obtain plant slurry; (4) degassing; (5) homogenizing; (6) sterilizing; (7) fermentation: naturally cooling to 40-45 DEG C, and adding 0.003-0.009 wt% of a leavening agent for fermentation; and (8) refrigerating and after-ripening. A pure plant fermentation system is adopted, cholesterol and animal fat are completely not contained, rich plant fibers and corn flavor are contained, and the set plant yoghurt is more suitable for lactose intolerant groups.

Description

Technical Field

[0001] The present invention relates to the technical field of yogurt preparation, and more particularly to a novel plant-based yogurt and a preparation method thereof. Background Art

[0002] "Huajian No. 1" is a new variety of non-genetically modified special corn, characterized in that the dry basis oil content of corn kernels is as high as more than 27%, the protein content reaches more than 24%, the endosperm content is extremely low, and it contains more beneficial nutritional components such as oleic acid, VE, and sterols. It is the first new variety of super-high oil and high-protein corn approved in the country. The crude fat content in ordinary corn is 4.0% - 4.7%, the starch content is 71.0% - 75.0%, and the crude protein content is 9.6% - 9.8%. The protein content of "Huajian No. 1" corn is more than twice that of ordinary corn, and the fat content reaches 6 - 7 times.

[0003] Plant-based yogurt is quite different from animal-based yogurt in terms of nutrition. The nutritional components in the raw materials are insufficient. If no additional nutritional components are supplemented during production, it is very difficult for the final product to meet people's nutritional needs, especially the protein content cannot be compared with animal milk. The amino acid types of plant proteins are incomplete. Currently, only the amino acid types of soy protein are similar to those of cow's milk, and essential amino acids are lacking in other raw materials. Different raw materials have different functional characteristics. The nutrition can be made more balanced by mixing multiple raw materials for co-fermentation. For example, using grains such as oats and rice will produce high levels of carbohydrates and fiber, while using pseudocereals and legumes such as quinoa, lupin, lentils, and soybeans will produce high-value proteins. Mixing grains and legumes together can supplement each other's amino acids and maximize the bioavailability of amino acids through bioprocessing.

[0004] During the process of plant germination, proteins are degraded, increasing the content of small-molecule peptides and free amino acids, thereby improving the nutritional components in the product. Peng Lu compared germinated and non-germinated soy yogurt, and the results showed that germination reduced the content of protease inhibitors and anti-nutritional factors in soybeans, improved the fermentability, and the viable count of lactic acid bacteria increased by 5.17 times compared with the non-germinated group. The contents of soy isoflavones, total phenols, and vitamin B12 in the germinated group of soy yogurt were significantly increased. During the production and processing process, soluble nutrients (vitamins, minerals, soluble sugars, etc.), proteins, etc. in the raw materials will be lost, and the loss of nutritional components can be reduced by optimizing the processing method. As a substitute for animal-based yogurt, in order to meet consumers' demand for nutritional supplementation, it is necessary to fortify the nutrition of plant-based yogurt.

[0005] Therefore, developing a novel corn plant-based yogurt with high nutritional value and good flavor is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a new type of plant-based yogurt and its preparation method. It adopts a pure plant fermentation system, contains no cholesterol and animal fat at all, and is rich in plant fiber and corn flavor, being a more suitable solidified plant yogurt for lactose-intolerant groups.

[0007] In order to achieve the above object, the present invention provides a preparation method of a new type of plant-based yogurt, comprising the following steps:

[0008] (1) Select dry corn kernels without moldy grains, add water and boil, then time for 30 min for rehydration and swelling, fish out and rinse clean, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby;

[0009] (2) Add flavor protease, transglutaminase and α-amylase, mix evenly, and carry out enzymatic hydrolysis;

[0010] (3) After the enzymatic hydrolysis is completed, add glucose, white sugar, vegetable oil, gel protein, emulsifier and stabilizer, and mix evenly by high-speed shearing to obtain plant slurry;

[0011] (4) Degassing: Degas the plant slurry at 60 - 65 °C and 0.5 ± 0.2 Pa;

[0012] (5) Homogenization: Homogenize at 45 MPa for 3 min;

[0013] (6) Sterilization: Sterilize at 95 - 100 °C for 5 min;

[0014] (7) Fermentation: Naturally cool to 40 - 45 °C, and add 0.003 - 0.009 wt% of starter culture for fermentation;

[0015] (8) Cold storage and after-ripening: After the fermented micro-endosperm corn plant-based yogurt is quickly cooled to room temperature, refrigerate it at 4 °C for after-ripening for 12 h to obtain the micro-endosperm corn plant-based yogurt.

[0016] Preferably, the enzyme activity of the flavor protease is 5000 - 6000 U / g, and the enzyme activity of the transglutaminase is 100 - 200 U / g; the flavor protease: transglutaminase = 2:1, and the total addition amount is 0.05 - 1% of the mass of the corn slurry;

[0017] The enzyme activity of the α-amylase is 20000 U / g, and the addition amount is 0.10 - 0.3% of the mass of the corn slurry.

[0018] The beneficial effects of adopting the above technical solution are as follows: Flavor protease and transglutaminase can effectively reduce bitterness before fermentation, enhance the gel network structure of proteins, improve the texture of yogurt. The enzymatic hydrolysis products such as small molecule peptides and amino acids can also provide energy for lactic acid bacteria, promote their reproduction and acid production, improve the fermentability of yogurt, and shorten the time for yogurt to reach the fermentation end point; The enzymatic hydrolysis and liquefaction by α-amylase hydrolyzes part of the starch into dextrin and glucose, which can increase the sugar content available for fermentation in the corn fermentation medium, promote microbial acid production, improve the utilization rate of raw materials, and improve the texture of yogurt.

[0019] Preferably, in step (2), the enzymatic hydrolysis is carried out at 45-65 °C for 20-60 min, and the corn slurry is stirred 2-3 times during the enzymatic hydrolysis.

[0020] Preferably, in step (3), based on the mass of the primary enzymatic hydrolysis solution, the addition amounts of the glucose and white sugar are 4-8%, and the glucose:white sugar = 2:3;

[0021] The vegetable oil is 2-5%, the gel protein is 10-15%, the emulsifier is 0.1-0.5%, and the stabilizer is 0.2-0.4%.

[0022] Preferably, the vegetable oil includes one or two of coconut oil and palm oil.

[0023] Preferably, the gel protein contains soy protein isolate and pea protein, and the mass ratio of soy protein isolate to pea protein is 1:2.

[0024] Preferably, the emulsifier contains one or a combination of two or more of diacetyl tartaric acid esters of mono- and diglycerides, phospholipids, monoglyceride fatty acids, sucrose fatty acids, acetylated distarch phosphates, and hydroxypropyl distarch phosphates.

[0025] Preferably, the stabilizer contains one or a combination of two or more of pectin, gellan gum, sodium carboxymethyl cellulose, natural inulin, modified starch, microcrystalline cellulose, and sodium alginate.

[0026] Preferably, in step (7), the starter culture contains at least two or more mixed strains of Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus casei, Lactococcus lactis subsp. diacetylactis, Bifidobacterium longum, Lactobacillus helveticus, and Lactobacillus rhamnosus.

[0027] Preferably, in step (7), the fermentation is carried out at 40-45 °C for 3-7 h.

[0028] The present invention uses corn without strong gelling effect as the base, adds vegetable oil to increase the total fat content of the product, and greatly improves the gel properties of the product after cooling and ripening. It is also formulated with strong gelling protein, and the total protein content of the product is controlled at 3.0%-4.0% to achieve the curdling effect and obtain good gel and solidification effects.

[0029] As can be seen from the above technical solutions, compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0030] (1) The present invention completely uses plant-based materials to produce pure plant-fermented yogurt after fermentation, which does not contain lactose and provides more choices for people with lactose intolerance. Moreover, through the proportioning of stabilizers and the optimization of raw materials, the present invention can prevent the phenomena of fat floating and protein water separation in plant-based yogurt during a long storage period, improve the quality and texture shape of plant-based yogurt, and ensure the stability of the product shelf life.

[0031] (2) The protein content of the corn-based plant yogurt of the present invention is ≥3.0%, which is not inferior to that of ordinary animal yogurt. Moreover, the present invention is a pure plant-based yogurt that does not contain cholesterol, animal fat, and lactose, which not only provides another choice for people with lactose intolerance but also better meets the current consumers' demand for low-fat and healthy food.

[0032] (3) The corn syrup used in the present invention undergoes pre-fermentation, which can improve the bitterness of the corn-based plant, enhance the fermentability of the yogurt, shorten the time for the yogurt to reach the fermentation end point, increase the sugar content available for fermentation in the corn-based plant, promote the acid production of microorganisms, improve the utilization rate of raw materials, and improve the texture of the yogurt.

[0033] (4) The texture properties of the corn-based plant yogurt of the present invention are higher than those of commercially available flavored fermented milk, coconut-based yogurt, and soybean-based yogurt. Its water-holding capacity is higher than that of soybean-based and flavored fermented milk. The DPPH free radical scavenging rate and ABST + free radical scavenging rates are 87.92±1.21% and 16.87±0.08% respectively, which are significantly higher than those of the other three commercially available yogurts, and it has good antioxidant ability.

[0034] (5) The proportion of hydrocarbons in the corn-based plant yogurt of the present invention is higher than that of commercially available flavored fermented milk, coconut-based yogurt, and soybean-based yogurt, which is a unique aroma component of the micro-endosperm corn-based plant yogurt. Moreover, the overall aroma components of the corn-based plant yogurt are relatively rich, and the substances such as alcohols, aldehydes, acids, esters, and ketones are relatively evenly dispersed, and the aroma is more mellow. Description of the Drawings

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0036] Figure 1 Are the types (a) and relative contents (b) of four volatile flavor substances in yogurt. Specific embodiments

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] 1. Determination of protein content

[0039] According to the Kjeldahl method in GB 5009.5-2010 "National Food Safety Standard - Determination of Protein in Foods".

[0040] 2. Determination of fat content

[0041] According to the acid hydrolysis method in GB 5009.6-2016 "National Food Safety Standard - Determination of Fat in Foods".

[0042] 3. Determination of texture properties

[0043] Use a TA11 / 1000 probe to perform texture analysis on the hardness, elasticity, cohesiveness, chewiness, and adhesiveness of yogurt. Determination conditions: Select the TPA mode, TA11 / 1000 probe, target value: 10 mm, test speed: 1.0 mm / s; trigger point load: 5 g.

[0044] 4. Determination of antioxidant activity

[0045] (1) DPPH radical scavenging rate: Prepare a 0.2 mmol / L DPPH solution with absolute ethanol and dilute it to 0.15 mmol / L. Mix the 0.15 mmol / L DPPH solution and the sample solution or 95% ethanol (blank control) at a ratio of 1:1, shake well, and react in the dark at room temperature for 20 min. Then centrifuge the sample at 1400 rpm for 10 min at room temperature, take the supernatant, and measure the absorbance value A at 517 nm. The result calculation is shown in the formula.

[0046] (2) ABST + Free radical scavenging rate: Measured using a Solarbio kit, and the result calculation is shown in the formula.

[0047] DPPH / ABST + The formula for calculating the free radical scavenging rate is as follows, where A is the measured absorbance value:

[0048]

[0049] 5. Detection method for volatile flavor substances

[0050] (1) Sample pretreatment: Weigh an appropriate amount of the sample and place it in a 20 mL headspace vial. Add the internal standard 2-octanol, adjust its injection concentration to 5 mg / L, add saturated sodium chloride, heat at 80 °C for 30 min, then use a headspace microextraction injection needle to pierce into the headspace vial and continue heating for 30 min, and then desorb at the injection port at 250 °C for 5 min.

[0051] (2) Instrument settings: Chromatographic column: HP-5MS (30 m × 0.25 mm × 0.25 μm); Column temperature: Initial temperature 50 °C, hold for 2 min, increase to 180 °C at a rate of 5 °C / min and hold for 5 min, then increase to 250 °C at a rate of 10 °C / min and hold for 5 min; Injection port temperature: 250 °C; Transfer line temperature: 280 °C; Carrier gas flow rate: 1.0 mL / min; Split ratio: No split.

[0052] (3) Mass spectrometry conditions: Ion source temperature: 230 °C, quadrupole temperature: 150 °C, mass spectrometry: EI source, scanning mode: Full scan 40 - 600.

[0053] Example 1

[0054] A preparation method for a novel plant-based yogurt, comprising the following steps:

[0055] (1) Select dry corn kernels without moldy grains, add water and boil, then time for 30 min for rehydration and swelling, fish out and rinse clean, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby;

[0056] (2) Add flavor protease, transglutaminase, and α-amylase, mix evenly, and carry out enzymatic hydrolysis. Stir the corn slurry 2 - 3 times during enzymatic hydrolysis for fermentation; among them, the enzyme activity of flavor protease is 5500 U / g, the enzyme activity of transglutaminase is 200 U / g, flavor protease:transglutaminase = 2:1, and the total addition amount is 0.4% of the mass of the corn slurry; the enzyme activity of α-amylase is 20000 U / g, and the addition amount is 0.3% of the mass of the corn slurry.

[0057] (3) After the enzymatic hydrolysis is completed, add glucose, white sugar, vegetable oil, gel protein, emulsifier, and stabilizer, and mix evenly by high-speed shearing to obtain plant slurry;

[0058] Based on the mass of the primary enzymolysis solution: the addition amounts of glucose and white sugar are 4%, and glucose:white sugar = 2:3; the addition amounts of coconut oil and palm oil are 3%; the addition amounts of soy protein isolate and pea protein are 10%, and the mass ratio of soy protein isolate to pea protein is 1:2; the addition amount of emulsifier is 0.3%, and the addition amount of stabilizer is 0.3%. Among them, the emulsifier includes diacetyl tartaric acid ester of mono- and diglycerides, sucrose fatty acid ester, and acetylated distarch phosphate, and the stabilizer includes sodium carboxymethyl cellulose and natural inulin.

[0059] (4) Degassing: Degas the plant slurry at 65 °C and 0.5 ± 0.2 Pa.

[0060] (5) Homogenization: Homogenize at 45 MPa for 3 min.

[0061] (6) Sterilization: Sterilize at 95 °C for 5 min.

[0062] (7) Fermentation: Naturally cool to 45 °C, add 0.004 wt% of the starter, and ferment at 45 °C for 6 h. Among them, the starter is a mixed strain including Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus casei, Bifidobacterium longum, Lactobacillus helveticus, and Lactobacillus rhamnosus.

[0063] (8) Cold storage and after-ripening: After the micro-endosperm corn plant-based yogurt after fermentation is quickly cooled to room temperature, it is refrigerated and after-ripened at 4 °C for 12 h to obtain the micro-endosperm corn plant-based yogurt.

[0064] The total protein content in the product is measured to be 3.03%, and the total fat content is 1.9 ± 0.11%.

[0065] Example 2

[0066] A preparation method of a novel plant-based yogurt, comprising the following steps:

[0067] (1) Select dry corn kernels without mildew, add water and boil, time for 30 min for rehydration and swelling, fish out and rinse, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby.

[0068] (2) Add flavor protease, transglutaminase, and α-amylase, mix evenly, and carry out enzymolysis. Stir the corn slurry 2 - 3 times during enzymolysis for fermentation. Among them, the enzyme activity of flavor protease is 5500 U / g, the enzyme activity of transglutaminase is 200 U / g, flavor protease:transglutaminase = 2:1, and the total addition amount is 0.2% of the mass of the corn slurry; the enzyme activity of α-amylase is 20000 U / g, and the addition amount is 0.1% of the mass of the corn slurry.

[0069] (4) After the enzymatic hydrolysis is completed, glucose, white sugar, vegetable oil, gelatin protein, emulsifier and stabilizer are added, and they are mixed evenly by high-speed shearing to obtain a plant slurry;

[0070] Based on the primary enzymatic hydrolysis solution: the addition amounts of glucose and white sugar are 5%, and glucose:white sugar = 2:3; coconut oil is 2%; soy protein isolate and pea protein are 12%, and the mass ratio of soy protein isolate to pea protein is 1:2; the emulsifier is 0.2%, and the stabilizer is 0.2%. Among them, the emulsifier includes diacetyl tartaric acid ester of mono- and diglycerides, phospholipids and monoglyceride fatty acid esters, and the stabilizer includes pectin and gellan gum.

[0071] (4) Degassing: Degas the plant slurry at 65°C and 0.5±0.2 Pa;

[0072] (5) Homogenization: Homogenize at 45 MPa for 3 min;

[0073] (6) Sterilization: Sterilize at 95°C for 5 min;

[0074] (7) Fermentation: Naturally cool to 45°C, add 0.004 wt% of the starter, and ferment at 45°C for 6 h; among them, the starter is a mixed strain containing Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus casei, Bifidobacterium longum, Lactobacillus helveticus, Lactobacillus rhamnosus.

[0075] (8) Cold storage and after-ripening: After the micro-endosperm corn plant-based yogurt after fermentation is quickly cooled to room temperature, it is refrigerated and after-ripened at 4°C for 12 h to obtain the micro-endosperm corn plant-based yogurt.

[0076] The total protein content in the product is measured to be 3.25%, and the total fat content is 1.7±0.08%.

[0077] Example 3

[0078] A preparation method of a novel plant-based yogurt, comprising the following steps:

[0079] (1) Select dry corn kernels without moldy grains, add water and boil, then time for 30 min for rehydration and swelling, fish out and rinse clean, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby;

[0080] (2) Add flavor protease, transglutaminase and α-amylase, mix evenly, and carry out enzymatic hydrolysis. Stir the corn slurry 2-3 times during the enzymatic hydrolysis for fermentation; among them, the enzyme activity of the flavor protease is 5500 U / g, the enzyme activity of the transglutaminase is 200 U / g, flavor protease:transglutaminase = 2:1, and the total addition amount is 0.6% of the mass of the corn slurry; the enzyme activity of the α-amylase is 20000 U / g, and the addition amount is 0.3% of the mass of the corn slurry.

[0081] (5) After the enzymatic hydrolysis is completed, glucose, white sugar, vegetable oil, gelatin protein, emulsifier and stabilizer are added, and they are mixed evenly by high-speed shearing to obtain a plant slurry;

[0082] Based on the primary enzymatic hydrolysis solution: the addition amounts of glucose and white sugar are 6%, and glucose:white sugar = 2:3; coconut oil is 5%; soy protein isolate and pea protein are 15%, and the mass ratio of soy protein isolate to pea protein is 1:2; the emulsifier is 0.4%, and the stabilizer is 0.3%. Among them, the emulsifier contains monoglyceride and hydroxypropyl distarch phosphate, and the stabilizer contains modified starch.

[0083] (4) Degassing: Degas the plant slurry at 65 °C and 0.5 ± 0.2 Pa;

[0084] (5) Homogenization: Homogenize at 45 MPa for 3 min;

[0085] (6) Sterilization: Sterilize at 95 °C for 5 min;

[0086] (7) Fermentation: Naturally cool to 45 °C, add 0.007 wt% of the starter, and ferment at 45 °C for 6 h; among them, the starter is a mixed strain containing Streptococcus thermophilus, Bifidobacterium longum, Lactobacillus rhamnosus, and Lactococcus lactis subsp. diacetylactis.

[0087] (8) Cold storage and after-ripening: After the fermented micro-endosperm corn plant-based yogurt is rapidly cooled to room temperature, it is refrigerated at 4 °C for 12 h to obtain the micro-endosperm corn plant-based yogurt.

[0088] The total protein content in the product is measured to be 3.74%, and the total fat content is 2.2 ± 0.17%.

[0089] Example 4

[0090] A preparation method of a novel plant-based yogurt, comprising the following steps:

[0091] (1) Select dry corn kernels without mildew, add water and boil, then time for 30 min for rehydration and swelling, fish out and rinse clean, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby;

[0092] (2) Add flavor protease, glutamine transaminase and α-amylase, mix evenly, and carry out enzymatic hydrolysis. Stir the corn slurry 2 - 3 times during the enzymatic hydrolysis for fermentation; among them, the enzyme activity of flavor protease is 5500 U / g, the enzyme activity of glutamine transaminase is 200 U / g, flavor protease:glutamine transaminase = 2:1, and the total addition amount is 0.8% of the mass of the corn slurry; the enzyme activity of α-amylase is 20000 U / g, and the addition amount is 0.3% of the mass of the corn slurry.

[0093] (6) After the enzymatic hydrolysis is completed, glucose, white sugar, vegetable oil, gel protein, emulsifier and stabilizer are added, and they are mixed evenly by high-speed shearing to obtain a plant slurry;

[0094] Based on the primary enzymatic hydrolysate: the addition amounts of glucose and white sugar are 8%, and glucose:white sugar = 2:3; palm oil is 4%; soy protein isolate and pea protein are 13%, and the mass ratio of soy protein isolate to pea protein is 1:2; the emulsifier is 0.3%, and the stabilizer is 0.4%. Among them, the emulsifier includes monoglyceride, hydroxypropyl distarch phosphate and sucrose fatty acid ester, and the stabilizer includes microcrystalline cellulose and sodium alginate.

[0095] (4) Degassing: The plant slurry is degassed at 65 °C and 0.5 ± 0.2 Pa;

[0096] (5) Homogenization: Homogenize at 45 MPa for 3 min;

[0097] (6) Sterilization: Sterilize at 95 °C for 5 min;

[0098] (7) Fermentation: Naturally cool to 45 °C, add 0.009 wt% of the starter, and ferment at 45 °C for 6 h; among them, the starter is a mixed strain containing Lactobacillus casei, Lactococcus lactis subsp. diacetylactis, Bifidobacterium longum, Lactobacillus helveticus, and Lactobacillus rhamnosus.

[0099] (8) Cold storage and ripening: After the fermented micro-endosperm corn plant-based yogurt is quickly cooled to room temperature, it is refrigerated and ripened at 4 °C for 12 h to obtain the micro-endosperm corn plant-based yogurt.

[0100] The total protein content in the product is measured to be 3.3%, and the total fat content is 2.1 ± 0.12%.

[0101] Analyze the corn plant-based yogurt (A), soy-based yogurt (B), coconut-based yogurt (C), and cow milk yogurt (D) in Example 3.

[0102] Experiment 1: Texture property analysis of micro-endosperm corn plant-based yogurt and commercially available yogurts

[0103] As can be seen from Table 1, the overall texture properties and water-holding capacity of this yogurt A are better, and it is a spoonable set yogurt. Secondly is yogurt C; the overall texture properties of yogurt A and yogurt B are not very different. Stabilizers are added to both yogurt C and yogurt D, and the internal structure of the yogurt is relatively stable.

[0104] Table 1 Measurement results of texture properties and water-holding capacity of four yogurts

[0105]

[0106] Note: Different letters in the same row indicate significant differences in data (p < 0.05).

[0107] Experiment 2: Analysis of the antioxidant properties of micro-endosperm corn plant-based yogurt and commercially available yogurts

[0108] As can be seen from Table 2, at the same concentration of yogurt extract, the DPPH radical scavenging rates and ABST + radical scavenging rates of each yogurt were in the order of A > B > C > D. Among them, the radical scavenging ability of the micro-endosperm corn plant-based yogurt was significantly higher than that of the other three commercially available yogurts. There was no significant difference in the DPPH radical scavenging ability between the soy-based and coconut-based yogurts, and the milk-based yogurt had the weakest scavenging ability. The raw material composition may be the reason for the differences in the antioxidant properties of various yogurts. Plant raw materials usually contain antioxidant components such as polyphenolic compounds, phytic acid, tocopherols, and carotenoids. In addition, corn peptides have been proven to be bioactive substances with relatively strong antioxidant ability. The enzymatic hydrolysis treatment in the early stage of the corn fermentation substrate, combined with the action of microbial fermentation, increased the content of corn protein peptides in the yogurt, which was also one of the reasons for improving the antioxidant properties of the yogurt.

[0109] Table 2 Determination results of the radical scavenging rates of four yogurts

[0110]

[0111] Note: Different letters in the same row indicate significant differences in the data (p < 0.05).

[0112] Experiment 3: Analysis of the volatile flavor substances of micro-endosperm corn plant-based yogurt and commercially available yogurts

[0113] The flavor substances in the four yogurts were analyzed and identified by GC-MS. The volatile substances in the yogurts were automatically matched and retrieved using the NIST database. 69, 53, 57, and 72 volatile flavor substances were detected in the four yogurts respectively, mainly including alcohols, ketones, esters, aldehydes, hydrocarbons, etc. These substances constituted the unique fermented fragrance of the yogurt.

[0114] From Figure 1 it can be seen that the types of compounds detected in the micro-endosperm corn plant-based yogurt and the milk-based yogurt were relatively rich. In the micro-endosperm corn plant-based yogurt, 6 alcohols, 7 aldehydes, 9 acids, 8 esters, 8 ketones, 7 hydrocarbons, and 24 other compounds were detected. In the milk-based yogurt, 6 alcohols, 4 aldehydes, 11 acids, 20 esters, 11 ketones, 7 hydrocarbons, and 13 other compounds were detected. There were more ester compounds in the coconut-based yogurt, and the main compound in the soy-based yogurt was ketones. Compared with the plant-based yogurt, a higher content of ester compounds was detected in the milk-based yogurt.

[0115] Ketones are important flavor compounds in yogurt, which are produced by Lactobacillus bulgaricus through the EMP pathway using lactose during the pre-fermentation stage of yogurt. The combined action of ketone compounds will exhibit the unique flavor of fermented milk, such as the buttery flavor of 3-hydroxy-2-butanone, the creamy and caramel aroma of 2,3-pentanedione, and a nutty undertone. A relatively large number of ketone species, 11 in total, were detected in yogurt D. Yogurt A, B, and C contained 8, 9, and 6 ketone species respectively. However, the relative content of ketone compounds in yogurt B was the highest at 18.84%.

[0116] Acid compounds are also one of the main components of yogurt flavor substances. Palmitic acid unique to yogurt A gives yogurt a laurel oil aroma; the content of yogurt compounds in yogurt B is less, and higher contents of caprylic acid and capric acid were detected in both yogurt C and D, mainly presenting fruit and caramel flavors.

[0117] Ester compounds are mainly produced by fatty acid hydrolysis and microbial metabolism. The relative content ratios of ester compounds detected in the four yogurts were relatively high, 27.20%, 14.62%, 32.15%, and 13.14% respectively. Among them, the fat content in the raw materials of A and C was relatively high, which led to a relatively high content of ester compounds.

[0118] Aldehydes are an important class of substances that constitute the typical flavor of yogurt. Seven aldehyde substances were detected in yogurt A, and the main components were trans-2-octenal, nonanal, and trans-2-nonenal, with fatty, cucumber, aldehyde, and citrus-like odors; there were 2 in yogurt B, mainly trans-2,4-decadienal (fruity flavor); there were 2 in yogurt C, namely (S)-(-)-2-(methoxymethyl)-1-pyrrolidinecarboxaldehyde and furfural (bread flavor, sweet flavor), and a total of 4 were detected in yogurt D, with the main component being 2-butynyl acetal and a relative content of 8.74%.

[0119] Seven hydrocarbon substances were detected in the micro-endosperm corn plant-based yogurt, with a relative content of 7.42%, which was higher than that of the other three yogurts. Among them, the main components and contents of olefins were 5.36% dicyclopentadiene and 0.29% dimer.alpha.-phellandrene. Dicyclopentadiene gave the micro-endosperm corn plant-based yogurt a fresh orange aroma and a lemon-like aroma.

[0120] Due to different raw materials, there are significant differences in the types and contents of flavor substances in the four yogurts. The overall aroma components of the micro-endosperm corn plant-based yogurt are relatively rich, and the contents of alcohols, aldehydes, acids, esters, and ketones are relatively evenly distributed, making the aroma more mellow. Under the combined action of all volatile components, the micro-endosperm corn plant-based yogurt presents a unique flavor.

[0121] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

Claims

1. A preparation method of a novel plant-based yogurt, characterized in that, It includes the following steps: (1) Select dry corn kernels without moldy grains, boil them in water, time for 30 min for rehydration and swelling, fish them out, rinse them clean, add pure water 8 times the mass of the dry corn kernels, and wet grind to obtain corn slurry for standby; (2) Add flavor protease, transglutaminase and α-amylase, mix evenly, and carry out enzymatic hydrolysis; (3) After the enzymatic hydrolysis is completed, add glucose, white sugar, vegetable oil, gel protein, emulsifier and stabilizer, and mix evenly by high-speed shearing to obtain plant slurry; (4) Degassing: Degas the plant slurry at 60 - 65 °C and 0.5 ± 0.2 Pa; (5) Homogenization: Homogenize at 45 MPa for 3 min; (6) Sterilization: Sterilize at 95 - 100 °C for 5 min; (7) Fermentation: Naturally cool to 40 - 45 °C, and add 0.003 - 0.009 wt% of starter culture for fermentation; (8) Cold storage and after-ripening: After the micro-endosperm corn plant-based yogurt after fermentation is quickly cooled to room temperature, refrigerate it at 4 °C for after-ripening for 12 h to obtain micro-endosperm corn plant-based yogurt.

2. The preparation method of a novel plant-based yogurt according to claim 1, wherein, In step (2), the enzyme activity of the flavor protease is 5000 - 6000 U / g, and the enzyme activity of the transglutaminase is 100 - 200 U / g; the flavor protease: transglutaminase = 2:1, and the total addition amount is 0.05 - 1% of the mass of the corn slurry; The enzyme activity of the α-amylase is 20000 U / g, and the addition amount is 0.10 - 0.30% of the mass of the corn slurry.

3. The preparation method of a novel plant-based yogurt according to claim 1, characterized in that, In step (2), the enzymatic hydrolysis is carried out at 45 - 65 °C for 20 - 60 min, and the corn slurry is stirred 2 - 3 times during the enzymatic hydrolysis.

4. The preparation method of a novel plant-based yogurt according to claim 1, characterized in that, In step (3), based on the mass of the primary enzymatic hydrolysis solution, the addition amounts of the glucose and the white sugar are 4 - 8%, and the glucose: white sugar = 2:3; The vegetable oil is 2 - 5%, the gel protein is 10 - 15%, the emulsifier is 0.1 - 0.5%, and the stabilizer is 0.2 - 0.4%.

5. The preparation method of a novel plant-based yogurt according to claim 4, characterized in that, The vegetable oil includes one or both of coconut oil and palm oil.

6. The preparation method of a novel plant-based yogurt according to claim 4, characterized in that, The gel protein includes soy protein isolate and pea protein, and the mass ratio of soy protein isolate to pea protein is 1:

2.

7. The preparation method of a novel plant-based yogurt according to claim 4, characterized in that, The emulsifier includes one or a combination of two or more of diacetyl tartaric acid ester of mono- and diglycerides, phospholipids, monoglyceride fatty acid esters, sucrose fatty acid esters, acetylated distarch phosphate, and hydroxypropyl distarch phosphate.

8. The preparation method of a novel plant-based yogurt according to claim 4, characterized in that, The stabilizer includes one or a combination of two or more of pectin, gellan gum, sodium carboxymethyl cellulose, natural inulin, modified starch, microcrystalline cellulose, and sodium alginate.

9. The preparation method of a novel plant-based yogurt according to claim 1, characterized in that, In step (7), the starter culture includes at least two mixed strains of Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus casei, Lactococcus lactis subsp. diacetylactis, Bifidobacterium longum, Lactobacillus helveticus, and Lactobacillus rhamnosus.

10. The preparation method of a novel plant-based yogurt according to claim 1, characterized in that, In step (7), the fermentation is carried out at 40 - 45 °C for 3 - 7 h.

Images